Sunlight-Driven Photothermally Boosted Photocatalytic Eradication of Superbugs Using a Plasmonic Gold Nanoparticle-Decorated WO3 Nanowire-Based Heterojunction

Abstract

Superbug infections are currently one of the biggest global health problems in our society. Herein, we report the design of a plasmonic gold nanoparticle (GNP)-decorated WO₃ nanowire-based heterojunction for the proficient usage of sunlight-based renewable energy to inactivate 100% superbugs via photothermally boosted photocatalytic action. Additionally, a synergistic photothermal and photocatalytic approach has been used for sunlight-driven complete eradication of carbapenem-resistant Enterobacteriaceae Escherichia coli (CRE E. coli) and methicillin-resistant Staphylococcus aureus (MRSA) superbugs. Interestingly, photocatalytic activity of methylene blue (MB) dye degradation in the presence of 670 nm near-infrared light shows that photothermally boosted photocatalytic performance is much superior to that of only a photocatalytic or photothermal process. The observed higher photocatalytic performance for the heterojunction is because the plasmonic GNP enhanced the absorption capability at 670 nm and increased the temperature of the photocatalyst surface, which reduces the activation energy of the degradation reaction. Similarly, sunlight-driven photocatalytic experiments show 100% degradation of MB after 60 min of sunlight irradiation. Moreover, sunlight-based photocatalytic inactivation of MRSA and CRE E. coli experiments show 100% inactivation after 60 min of light irradiation.

Figure 1

(A) Schematic representation shows the possible pathway for the sunlight-driven photothermally boosted photocatalytic degradation of MB dye using a plasmonic GNP-decorated WO₃ nanowire-based heterojunction catalyst. (B) Schematic representation shows the possible pathway for the sunlight-driven photothermally boosted photocatalytic inactivation of superbugs using a plasmonic GNP-decorated WO₃ nanowire-based heterojunction catalyst.

Figure 2

Schematic representation shows the design steps we have used for the synthesis of the spherical GNP-decorated WO₃ nanowire-based heterojunction. (A) Synthesis of spherical GNPs. (B) Solvothermal synthesis of WO₃ nanowires. (C) Development of the GNP-decorated WO₃ nanowire-based heterojunction.

Figure 3

(A) TEM image of freshly prepared spherical GNPs with a diameter of 25 ± 2 nm. (B) TEM image of freshly prepared WO₃ nanowires. (C) SEM image of freshly prepared WO₃ nanowires. (D) TEM image of the freshly prepared GNP-decorated WO₃ nanowire-based heterojunction. (E) SEM image of the freshly prepared GNP-decorated WO₃ nanowire-based heterojunction. 2D r-GO-attached 1D WO₃ nanowire-based heterostructure. (F) XRD patterns from the heterojunction shows the Au (111), (200), and (220) planes for the GNP and (020), (120), (112), and (222) planes for WO₃. (G) EDX spectrum of the heterojunction shows the presence of Au, O, and W. (H) Absorption spectra of the spherical GNP, WO₃ nanowire, and heterojunction. (I) Raman spectra of the WO₃ nanowire and heterojunction show the presence of O–W–O stretching and bending, W–O symmetric stretching, and W–O asymmetric stretching bands from WO₃.

Figure 4

(A) Change of the absorption spectra of MB after exposure to 670 nm light for 20 min without the catalyst and with the WO₃ nanowire, GNP, and heterojunction catalyst. (B) Change of fluorescence spectra of MB after exposure to 670 nm light for 20 min without the catalyst and with the WO₃ nanowire, GNP, and heterojunction catalyst. (C) Time-dependent fluorescence intensity changes for MB during the exposure of 670 nm light in the presence of the heterojunction catalyst. (D) Time-dependent absorption intensity changes for MB during exposure to 670 nm light in the presence of the heterojunction catalyst. (E) Plot shows complete degradation of MB after exposure to 670 nm light for 25 min in the presence of the heterojunction catalyst. (F) Photograph shows IR thermography images of buffer in the presence of the WO₃ nanowire, GNP, and heterojunction catalyst when they are exposed to 670 nm NIR light for 15 min. (G) Degradation percentage changes with time for MB during the exposure to 670 nm light without the catalyst and with the WO₃ nanowire, GNP, and heterojunction catalyst. (H) Degradation percentage changes with time for MB during 670 and 532 nm light and sunlight exposure in the presence of the heterojunction catalyst. (I) Plot shows how the presence of different scavengers changes the degradation percentage of MB during 670 nm light exposure with the heterojunction catalyst.

Figure 5

(A) MRSA inactivation efficiency after exposure to 670 nm light for 20 min in the presence of the WO₃ nanowire, GNP, and heterojunction catalyst. (B) MRSA inactivation efficiency in the presence of sunlight at different time intervals when the heterojunction catalyst is present. (C) Biocompatibility of the heterojunction catalyst against different cells in the absence of light. (D) MRSA inactivation efficiency in the presence of the heterojunction catalyst without light, only light, light with the heterojunction catalyst, GNPs catalyst, and WO₃ nanowire catalyst. (E) Relative cellular ATP leakage percentage from MRSA in the presence of the heterojunction catalyst without light, with light only, and with light in the presence of the heterojunction catalyst, GNPs catalyst, and WO₃ nanowire catalyst. (F) Plot shows time-dependent superbug inactivation efficiency in the presence of sunlight and the heterojunction catalyst. (G) Plot shows time required for 100% MRSA inactivation in the presence of 670 and 532 nm light and sunlight using the heterojunction catalyst. (H) Plot shows time required for 100% of CRE E. coli inactivation in the presence of 670 and 532 nm light and sunlight using the GNPs-decorated WO₃ nanowire heterojunction catalyst. (I) TEM image shows that heterojunction wraps the MRSA bacterial surface. (J) SEM image shows high membrane damage on the superbug surface when MRSA bacteria are exposed to sunlight and heterojunction catalysts for 60 min. (K) SEM image shows high membrane damage on the superbug surface when CRE E. coli bacteria are exposed to sunlight and heterojunction catalysts for 60 min.